Root Cause Analysis Of The Instable Vibration Behavior On A 850MW Large Steam Turbo-unit

A abnormal running condition of a 840MW large turbo-unit, characterized withinstable vibration, was studied by means of morden vibration analysis and diagnosistechnique. The vibration signals of the turbine by start-up and shut-down and by variesload-changed conditions were measured on-line with the help of a self-developedvibration monitoring system. Based on the classic vibration analysis methods such astime domain analysis and spetrum analysis and the holospectrum method, the relativeshaft vibration and absolute bearing box vibration of the turbine was analyzied. The rootcause of the failure was diagnosed.